clang-format: Prevent column layout if elements aren't uniform enough.

This patch only considers the difference between the length of the
shortest and longest element, but we might want to look at other
features (token count, etc.) in future.

Before:
  std::vector<MyValues> aaaaaaaaaaaaaaaaaaa{
      aaaaaaa,      aaaaaaaaaa,
      aaaaa,        aaaaaaaaaaaaaaa,
      aaa,          aaaaaaaaaa,
      a,            aaaaaaaaaaaaaaaaaaaaa,
      aaaaaaaaaaaa, aaaaaaaaaaaaaaaaaaa + aaaaaaaaaaaaaaaaaaa,
      aaaaaaa,      a};

After:
  std::vector<MyValues> aaaaaaaaaaaaaaaaaaa{
      aaaaaaa, aaaaaaaaaa, aaaaa, aaaaaaaaaaaaaaa, aaa, aaaaaaaaaa, a,
      aaaaaaaaaaaaaaaaaaaaa, aaaaaaaaaaaa,
      aaaaaaaaaaaaaaaaaaa + aaaaaaaaaaaaaaaaaaa, aaaaaaa, a};

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@218111 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Format/FormatToken.cpp b/lib/Format/FormatToken.cpp
index c6f23a6c281b5491e2f2a0152504aba690589099..677f1a0bb131717954ad7488446a351565ae3186 100644 (file)
--- a/lib/Format/FormatToken.cpp
+++ b/lib/Format/FormatToken.cpp
@@ -145,6 +145,9 @@ void CommaSeparatedList::precomputeFormattingInfos(const FormatToken *Token) {
   // trailing comments which are otherwise ignored for column alignment.
   SmallVector<unsigned, 8> EndOfLineItemLength;
 
+  unsigned MinItemLength = Style.ColumnLimit;
+  unsigned MaxItemLength = 0;
+
   for (unsigned i = 0, e = Commas.size() + 1; i != e; ++i) {
     // Skip comments on their own line.
     while (ItemBegin->HasUnescapedNewline && ItemBegin->isTrailingComment())
@@ -171,6 +174,9 @@ void CommaSeparatedList::precomputeFormattingInfos(const FormatToken *Token) {
       ItemEnd = Commas[i];
       // The comma is counted as part of the item when calculating the length.
       ItemLengths.push_back(CodePointsBetween(ItemBegin, ItemEnd));
+      MinItemLength = std::min(MinItemLength, ItemLengths.back());
+      MaxItemLength = std::max(MaxItemLength, ItemLengths.back());
+
       // Consume trailing comments so the are included in EndOfLineItemLength.
       if (ItemEnd->Next && !ItemEnd->Next->HasUnescapedNewline &&
           ItemEnd->Next->isTrailingComment())
@@ -186,8 +192,10 @@ void CommaSeparatedList::precomputeFormattingInfos(const FormatToken *Token) {
 
   // If this doesn't have a nested list, we require at least 6 elements in order
   // create a column layout. If it has a nested list, column layout ensures one
-  // list element per line.
-  if (HasNestedBracedList || Commas.size() < 5 || Token->NestingLevel != 0)
+  // list element per line. If the difference between the shortest and longest
+  // element is too large, column layout would create too much whitespace.
+  if (HasNestedBracedList || Commas.size() < 5 || Token->NestingLevel != 0 ||
+      MaxItemLength - MinItemLength > 10)
     return;
 
   // We can never place more than ColumnLimit / 3 items in a row (because of the

diff --git a/unittests/Format/FormatTest.cpp b/unittests/Format/FormatTest.cpp
index 93c58348a5f1a26644a022c251e58479e88bda2e..44429031d8977d74777deb29b1dced152576442f 100644 (file)
--- a/unittests/Format/FormatTest.cpp
+++ b/unittests/Format/FormatTest.cpp
@@ -5631,15 +5631,11 @@ TEST_F(FormatTest, LayoutCxx11BraceInitializers) {
       "std::this_thread::sleep_for(\n"
       "    std::chrono::nanoseconds{ std::chrono::seconds{ 1 } } / 5);",
       ExtraSpaces);
-  verifyFormat("std::vector<MyValues> aaaaaaaaaaaaaaaaaaa{\n"
-               "  aaaaaaa,      aaaaaaaaaa,\n"
-               "  aaaaa,        aaaaaaaaaaaaaaa,\n"
-               "  aaa,          aaaaaaaaaa,\n"
-               "  a,            aaaaaaaaaaaaaaaaaaaaa,\n"
-               "  aaaaaaaaaaaa, aaaaaaaaaaaaaaaaaaa + aaaaaaaaaaaaaaaaaaa,\n"
-               "  aaaaaaa,      a\n"
-               "};",
-               ExtraSpaces);
+  verifyFormat(
+      "std::vector<MyValues> aaaaaaaaaaaaaaaaaaa{\n"
+      "    aaaaaaa, aaaaaaaaaa, aaaaa, aaaaaaaaaaaaaaa, aaa, aaaaaaaaaa, a,\n"
+      "    aaaaaaaaaaaaaaaaaaaaa, aaaaaaaaaaaa,\n"
+      "    aaaaaaaaaaaaaaaaaaa + aaaaaaaaaaaaaaaaaaa, aaaaaaa, a};");
   verifyFormat("vector<int> foo = { ::SomeGlobalFunction() };", ExtraSpaces);
 }